San Diego  Trius Therapeutics said Wednesday it has raised about $34 million from a secondary stock offering. The biotech company is testing an antibiotic to treat a "superbug" bacterial infection resistant to most existing drugs.

Trius said it intends to use the money for clinical trials of the antibiotic, tedizolid phosphate, other research and development expenses, and for general purposes. Tedizolid is being tested to treat infections of methicillin-resistant Staphylococcus aureus, known as MRSA.

It is scheduled to close on or about Thursday, Trius said. Proceeds include sales from an option exercised by the underwriters to buy an extra 869,000 shares.

With the sale of the additional shares, Trius said it will have sold a total of 7,169,000 shares at $4.75 apiece. Trius closed Wednesday after the announced at $4.92, down 6 cents for the day.

Earlier this month, Trius said the U.S. Food and Drug Administration had given tedizolid marketing incentives, including priority review when the drug approval application is submitted, and five additional years of marketing exclusivity.